Wood chip



Aug. 6, 1968 K. c. LOGAN ETAL 3,396,069

WOOD CHIP Filed Nov. 20, 1964- PATENT AGENT United States Patent 3,396,069 WOOD CHIP Kenneth C. Logan and Ola Sepall, Quebec, Quebec,

Canada, assignors to Anglo Paper Products, Limited, Quebec, Quebec, Canada I Continuation-in-part of abandoned application Ser. No. 258,697, Feb. 15, 1963. This application Nov. 20, 1964, Ser. No. 412,795

6 Claims. (Cl. 161-117) ABSTRACT OF THE DISCLOSURE Wood chips for paper making pulp each being of curved contour whereby one major surface is convexly curved and the other major surface is concavely curved, there being a plurality of cracks in the convexly curved surface extending in the grainwise direction of the wood. Each chip has a thickness of about 0.1 to about 0.3 inch and a maximum dimension from end to end and from side to side of six inches.

This invention relates to wood chips for use in the production of pulp for paper making. This application is a continuation-in-part of patent application Ser. No. 258,697, filed Feb. 15, 1963, now abandoned.

It has long been recognized that the characteristics of chips as produced for pulping have a very substantial effect upon the quality of the resulting pulp. One of the most important of these characteristics is the fiber condition of the chips employed. If the fibers in the chips are in damaged condition, the resulting pulp will be of lower quality depending upon the extent of fiber damage in the chi s.

i nother factor that has a substantial bearing upon pulp quality is the dimensional characteristic of the chip. The most important dimension is that of thickness. If the chip is excessively thin it will be overcooked. If it is too thick, it will not be cooked in the center and pulp screen rejects will be high.

It is also highly desirable, for uniform pulp quality, that the chips employed conform to certain uniform characteristics including size.

It is an object of this invention to provide a wood chip for pulping which possesses desirable shape, size and other characteristics whereby there is achieved better uniformity in pulp production with consequent greater yield of good quality pulp and less reject material.

Another object of the invention is to provide a wood chip for pulping the fibers of which have minimal damage as compared with the natural state thereof whereby pulp produced therefrom is of higher grade.

The invention resides in a wood chip for pulping which comprises a body having two major side surfaces in opposed relation to each other and substantially uniformly spaced from each other, two side edge surfaces, and two end edge surfaces, each of the side edge surfaces being approximately at right angles to the grain of the wood in the body whereby the grain extends substantially transversely of the major side surfaces. The space between the major side surfaces is about 0.065 to 0.500 inch. The chip is curled somewhat, one of the major side surfaces being convexly curved and the other being concavely curved. The convexly curved surface has therein a plurality of cracks extending from one to the other of the side edge surfaces. Each of the side edge surfaces is disposed at a specified angle of 85 to to one of the major side surfaces.

Further, in accordance with the invention, the fibers in the chip body are compressed in the grainwise direction thereof less than 0.060 inch per inch as compared with the natural condition of the fibers.

3,396,069 Patented Aug. 6, 1968 The invention will be described with reference to the accompanying drawing, in which FIGURE 1 is a plan view of a chip in accordance with the invention,

FIGURE 2 is a side elevation, and

FIGURE 3 is an end elevation.

Referring to the drawing, the chip 10 has two major side surfaces 11 and 12, surface 11 being convexly curved and surface 12 being concavely curved. The chip also has two side edge surfaces 13 and two end edge surfaces 14. The grain or fiber direction of the chip, as indicated at 15, extends transversely of the major side surfaces 11 and 12, that is; substantially right angularly with respect to side edge surfaces 13.

The thickness of the chip, that is; the distance between the major side surfaces 11 and 12, is substantially uniform throughout and about 0.1 to 0.3 inch.

It has been found that the selection of chips of the specified thickness is necessary for most effective pulp production. As previously indicated, chips of a thickness above about 0.3 inch are unsuitable because pulp screen rejects are unduly high. Use of chips having a thickness below about 0.1 inch is undesirable because the bulk density is reduced and, furthermore, the production capacity of batch pulping equipment is reduced.

The chip dimension in the grainwise direction thereof, that is, the distance between side edge surfaces 13 may range from about /2 to 6 inches.

The chip dimension in the crossgrain direction thereof, that is, the distance between end edge surfaces 14, may range from about one to six inches.

The chip employed in accordance with the invention is somewhat curled as shown in the drawing, that is, the surface 11 is convexly curved and the surface 12 is concavely curved. Such a curled chip has a plurality of transverse cracks 16 in the surface 11 thereof, each such crack extending substantially from one to the other of edge surfaces 13. These cracks occur at a spacing of not substantially more than one-quarter inch. Moreover, since the thickness of the chip will not substantially exceed 0.3 inch, the depth of each crack is substantially greater than one-half of such thickness.

The presence of the grainwise splitting or cracking condition of the chip is of significant importance since it results in the presentation of a greatly enlarged chip surface area for penetration of pulping chemicals with consequent more uniform reaction conditions.

Each side edge surface 13 is disposed at an angle of to 5 to the major side surface 12. It has been found that when the chip has been formed by cutting at such an angle (indicated at A in FIGURE 3) to produce such side edge surfaces, fiber damage is reduced.

The invention further resides in selecting a chip having not only the aforementioned characteristics but one in which there is granwise compression less than 0.060 inch per inch as compared with the natural conditions of the fibers in the chip. By natural condition as employed in this specification and claims is meant the condition of the particular fibers in the log before the chip was cut therefrom.

It has been found that, if the fibers of the chip are not more greatly compressed than 0.060 inch per inch of wood, the fiber damage is not of great consequence and pulp produced therefrom will be of uniformly high quality.

Sulphite pulp prepared from chips produced in accordance with the invention has much superior qualities as compared with sulphite pulp prepared from chips produced by presently available commercial chippers. The following tables give the results of comparison tests, column numbered (1) being values relating to regular pulp prepared from chips produced in conventional commer- 3 cial manner and column numbered (2) being values relating to pulp prepared from chips produced in accordance with the invention.

A. BLEACHED SULPHITE PULPS Beater Evaluation-Properties at 300 (1) 0.8. Freeness:

Burst Factor 51 67 Tear Factor. 67 .72 Breaking Leng meters) 400 10, 200 Dynamic Breaking Stress (era/kg)-.- 1. 6 2. Static Breaking Stress (kg) 7. 7 8.8 Stretch (rnrn.) 2.9 3.4 Bulk (cc./g.)- 1.29 1. 28 Beating Time (min.) 54 40 Fiber Length Classification Percent:

Retained on 14 mesh 4. 11.2 Retained on 30 mesh 31. 6 40. 3 Retained on 100 mesh 29. 9 24. 8 Percent Fines (pass 100 mesh) 34. 0 23. 7 Ball Mill Evalutation-Properties at 30 0.8. Freeness:

Burst Factor 48 58 Breaking Length (meters).. 7, 600 9, 000 Fold (M.I.T.) 240 1,000 Beating Time (min) 144 144 Fiber Length Classification Percent:

Retained on 14 mesh 21.1 34. 3 Percent Fines (pass 100 mesh) 22. 6 6. 5

B. UNBLEACHED SULPHITE PULPS Properties at 300 0.8. FreenessHeater Pulp Test:

Burst Factor 00-65 76-80 Tensile, Breaking Length 10, 550- 12, 000- 11, 000 12, 500 Impact Tensile 9, 700 10,800 Porosity (relative 1.0 0.5 Double folds 200 600 Percent long fibers (retained on N 14 mesh) 5-20 2441 Resistance to Mechanical Damage:

Percent long fibers (retained on N o.

14 mesh) in untreated pulp 41 Percent long fibers (retained on N o. 14 mesh) in pulp treated Waring Blendor 11 29 Resistance to Acid Hydrol Percent long fiber (retained on No.

14 mesh) after hydrolysis in 0.25 N. sulphuric at 100 C 19 33 Same as above after tre ent in Waring Blender 2 4 Percent long fibers retanied in No. mesh in above pulp after treatment in Waring Blendor We claim: 1. A wood chip for production of papermaking pulp which comprises a body having two major side surfaces 4. in opposed relation to each other and substantially uniformly spaced from each other, two sideedge surfaces,

and two end edge surfaces, each of said side edge surfaces being approximately at right angles to the grain of the wood in said body whereby said grain extends substantially transversely of said major side surfaces, said major side surfaces being spaced from each other about 0.1 to 0.3 inch, the distance between said side edge surfaces and between said end edge surfaces being not substantially greater than six inches, one of said major side surfaces being convexly curved and the other of said major side surfaces being concavely curved, said convexly curved surface having therein a plurality of cracks extending from one to the other of said side edge surfaces, each of said side edge sur-- faces being disposed at a specified angle of 85 to 5 to one of said major side surfaces.

2. A wood chip for pulping as defined in claim 1, each said crack being spaced from an adjacent crack. less than about one-quarter inch.

3. A wood chip for pulping as defined in claim 2, each said crack having a depth at least half the distance between said major side surfaces.

4. A wood chip for pulping as defined in claim 1, the fibers in said body being compressed in the grainwise direction thereof less than 0.060 inch per inch as compared with the natural condition of said fibers.

5. A wood chip for pulping as defined in claim 1, said angle being to 15.

6. A wood chip for pulping as defined in claim 1, the distance between said side edge surfaces being one-half to six inches, the distance between said end edge surfaces being one to six inches.

References Cited UNITED STATES PATENTS 1,427,812 9/1922 Hirt 1611l7 1,819,775 8/1931 Elmendorf 16l-l 17 2,452,226 10/1948 Cone 16l1 17 2,751,947 6/1956 Wyss 161168 2,773,789 12/1956 Clark 161168 2,854,372 9/1958 Yan et al. 161-168 MORRIS SUSSMAN, Primary Examiner. 

